Hybrid gmp/equalizer digital self interference cancelation for mimo transmitters

ABSTRACT

A base station configured to perform a method for self-interference cancelation (SIC) is provided. The method includes transmitting, by a transceiver configured to transmit an uplink channel and a downlink channel concurrently, one or more signals, the transceiver coupled to, or including, a first number of transmit antennas and a second number of receive antennas. The method also includes, for at least one receive antenna of the second number of receive antennas, applying a forward path model including a non-linear component corresponding to a transmit path in the transceiver, and applying an equalizer function to a first signal to be transmitted by at least one transmit antenna of the first number of transmit antennas determine a self-interference (SI) estimate; and subtracting, in SIC circuitry, the SI estimate from the signal received via at least one receive antenna of the second number of receive antennas to obtain an residual signal.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application claims priority to U.S. Provisional PatentApplication No. 63/171,333 filed on Apr. 6, 2021. The content of theabove-identified patent document is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to wireless communicationsystems and, more specifically, the present disclosure relates to anequalizer assisted self-interference canceler for multi-antenna systems.

BACKGROUND

Traditionally, modern cellular communication systems operate within twomain modes; Time Division Duplexing (TDD) and Frequency DivisionDuplexing (FDD). There are several tradeoffs between TDD and FDDsystems. TDD systems split uplink (UL) and downlink (DL) in the timedomain, while FDD systems split uplink and downlink in frequency domain.Therefore, UL in TDD system operates at a duty cycle (less than 100% oftime) while UL in FDD system operates 100% of time but requires aseparate band. Furthermore, FDD system requires isolation betweentransmit (TX) and receive (RX) as both are operated simultaneously. Theisolation is achieved using duplexers and/or separate antennas.

SUMMARY

The present disclosure relates to wireless communication systems and,more specifically, the present disclosure relates to an equalizerassisted self-interference canceler for a multi-antenna system.

In one embodiment, an apparatus is provided. The apparatus includes atransceiver configured to communicate via an uplink channel and adownlink channel concurrently. The apparatus also includes a firstnumber of transmit antennas, a second number of receive antennas, anequalizer, and self-interference cancel (SIC) circuitry. The equalizeris configured to, for at least one receive antenna of the second numberof receive antennas, apply a forward path model including a non-linearcomponent corresponding to a transmit path in the transceiver, and applyan equalizer function to a first signal to be transmitted by at leastone transmit antenna of the first number of transmit antennas todetermine a self-interference (SI) estimate. The SIC circuitryconfigured to, for the at least one receive antenna of the second numberof receive antennas, subtract the SI estimate from the signal receivedvia at least one receive antenna of the second number of receiveantennas to obtain an residual signal.

In another embodiment, a method is provided. The method includestransmitting, by a transceiver configured to transmit an uplink channeland a downlink channel concurrently, one or more signals, thetransceiver coupled to, or including, a first number of transmitantennas and a second number of receive antennas. The method alsoincludes, for at least one receive antenna of the second number ofreceive antennas, applying a forward path model including a non-linearcomponent corresponding to a transmit path in the transceiver, andapplying an equalizer function to a first signal to be transmitted by atleast one transmit antenna of the first number of transmit antennasdetermine a self-interference (SI) estimate; and subtracting, in aself-interference cancel (SIC) circuitry, the SI estimate from thesignal received via at least one receive antenna of the second number ofreceive antennas to obtain an residual signal.

In yet another embodiment, a non-transitory computer readable medium isprovided. The non-transitory computer readable medium a plurality ofinstructions that, when executed by at least one processor, cause theprocessor to transmit, by a transceiver configured to transmit an uplinkchannel and a downlink channel concurrently, one or more signals, thetransceiver coupled to, or including, a first number of transmitantennas and a second number of receive antennas. The instructionsfurther cause the processor to, for at least one receive antenna of thesecond number of receive antennas, applying a forward path modelincluding a non-linear component corresponding to a transmit path in thetransceiver, and applying an equalizer function to a first signal to betransmitted by at least one transmit antenna of the first number oftransmit antennas determine a self-interference (SI) estimate; andsubtracting, in a self-interference cancel (SIC) circuitry, the SIestimate from the signal received via at least one receive antenna ofthe second number of receive antennas to obtain an residual signal.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example gNB according to embodiments of thepresent disclosure;

FIG. 3 illustrates an example UE according to embodiments of the presentdisclosure;

FIG. 4A illustrates a high-level diagram of an orthogonal frequencydivision multiple access transmit path according to embodiments of thepresent disclosure;

FIG. 4B illustrates a high-level diagram of an orthogonal frequencydivision multiple access receive path according to embodiments of thepresent disclosure;

FIG. 5 illustrates an example antenna according to embodiments of thepresent disclosure;

FIG. 6 illustrates examples of a time-division duplex (TDD)communication and a cross-division duplex (XDD) communication accordingto embodiments of the present disclosure;

FIG. 7 illustrates an example of a multiple antenna array according toembodiments of the present disclosure;

FIG. 8 illustrates examples of self-interference according toembodiments of the present disclosure;

FIG. 9 illustrates another example of a hybrid digital self-interferencecancelation transceiver according to embodiments of the presentdisclosure;

FIG. 10 illustrates another example of a hybrid digitalself-interference cancelation multi-antenna transceiver according toembodiments of the present disclosure;

FIG. 11 illustrates a state machine for operating mode transitionsaccording to embodiments of the present disclosure;

FIG. 12 illustrates a modeling process according to embodiments of thepresent disclosure;

FIG. 13 illustrates an example modelling system diagram according toembodiments of the present disclosure;

FIG. 14 illustrates a process for self-interference cancelationaccording to embodiments of the present disclosure; and

FIG. 15 illustrates an example SIC Operation System diagram according toembodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 through FIG. 15, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Aspects, features, and advantages of the disclosure are readily apparentfrom the following detailed description, simply by illustrating a numberof particular embodiments and implementations, including the best modecontemplated for carrying out the disclosure. The disclosure is alsocapable of other and different embodiments, and its several details canbe modified in various obvious respects, all without departing from thespirit and scope of the disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature, and not asrestrictive. The disclosure is illustrated by way of example, and not byway of limitation, in the figures of the accompanying drawings.

As indicated herein above, modern cellular communication systems operatewithin two main modes; Time Division Duplexing (TDD) and FrequencyDivision Duplexing (FDD) and there are several tradeoffs between TDD andFDD systems. Additionally, mobile terminals, such as user equipments(UEs) have limited output power, which can be 23 dBm in cellularcommunication links. The limited output power of the UEs can constrainthe coverage as the uplink (UL) power is distributed across an entirebandwidth (BW) for an allocated proportion of time. The power spectraldensity of output power is lower and reaches a lower distance; thereby,causing a lower coverage range, which can be an issue with cell siteplanning as more base stations are required to cover an area. TDDsystems are simpler to implement have the advantage of using just onechunk of band for both UL and downlink (DL). TDD does not requiredpaired bands for operation as TDD can use the entire band.

Embodiments of the present disclosure provide a transceiver architecturethat is configured to remove a leakage value, which occurs from atransmit signal, from a received signal. Certain embodiments of thepresent disclosure provide equalizer circuit before a self-interferencecanceler to alleviate a frequency response introduce by a channeldistortion occurring between a multiple transmit antennas and one ormore receive antennas.

Although exemplary descriptions and embodiments to follow assumeorthogonal frequency division multiplexing (OFDM) or orthogonalfrequency division multiple access (OFDMA), this disclosure can beextended to other OFDM-based transmission waveforms or multiple accessschemes such as filtered OFDM (F-OFDM).

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system, as well asnon-terrestrial networks (NTN). Therefore, the 5G or pre-5Gcommunication system is also called a “beyond 4G network” or a “post LTEsystem.” The 5G communication system is considered to be implemented inhigher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplishhigher data rates. To decrease propagation loss of the radio waves andincrease the transmission coverage, the beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesand the like are discussed in 5G communication systems.

In MIMO systems operating in XDD or FD modes, the transmit signal fromeach transmit antenna will interfere with each received signal at eachreceived antenna. Traditional self-interference cancelation solutionsused in single-input single-output (SISO) systems are not applicablebecause:

(1) Coupling can occur between the DL signal on a transmit antenna toall receive antennas receiving UL

(2) Multiple transmit signals interfere with the receive antennas witharbitrary time and phase offsets; and

(³) The coupling between a TX antenna and an RX antenna has a uniquefrequency response that depends on the location of the two antennas withrespect to each other as well as within the antenna panel.

Embodiments of the present disclosure provide a solution for estimationand cancelation of self-interference in MIMO systems—with application tomassive MIMO systems. This becomes particularly challenging whenconsidering the various couplings that might appear when simultaneouslyoperating on multiple antennas. Additionally, certain embodimentsaddress the shortcomings of our other proposed solution, providingcomparable SIC performance without the need of extra ADCs and traces forfeedback signals at a cost of increased digital processing complexity.

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA) communication techniques. The descriptions of FIGS. 1-3 are notmeant to imply physical or architectural limitations to the manner inwhich different embodiments may be implemented. Different embodiments ofthe present disclosure may be implemented in any suitably-arrangedcommunications system.

Certain embodiments of the disclosure may be derived by utilizing acombination of several of the embodiments listed below. Also, it shouldbe noted that further embodiments may be derived by utilizing aparticular subset of operational steps as disclosed in each of theseembodiments. This DOI should be understood to cover all suchembodiments.

Certain embodiments of the present disclosure are described assumingcellular DL communications. However, the same/similar principles andrelated signaling methods & configurations can also be used for cellularUL & sidelink (SL).

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure. The embodiment of the wireless network shownin FIG. 1 is for illustration only. Other embodiments of the wirelessnetwork 100 could be used without departing from the scope of thisdisclosure.

As shown in FIG. 1, the wireless network 100 includes a gNB 101, a gNB102, and a gNB 103. The gNB 101 communicates with the gNB 102 and thegNB 103. The gNB 101 also communicates with at least one core network130, such as the Internet, a proprietary Internet Protocol (IP) network,or other data network.

The gNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe gNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business; a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The gNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe gNB 103. The second plurality of UEs includes the UE 115 and the UE116 as well as a UE 117, which may be located in a third residence (R),and a UE 118, which may be located in another residence (R). In someembodiments, one or more of the gNBs 101-103 may communicate with eachother and with the UEs 111-118 using 5G, LTE, LTE-A, WiMAX, WiFi, orother wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point(AP), or other wirelessly enabled devices. Base stations may providewireless access in accordance with one or more wireless communicationprotocols, e.g., 5G 3GPP new radio interface/access (NR), long termevolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS”and “TRP” are used interchangeably in this patent document to refer tonetwork infrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, the term “userequipment” or “UE” can refer to any component such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” “receivepoint,” or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses a BS, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with gNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the gNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of gNB 101, gNB 102 andgNB 103 include a two-dimensional (2D) antenna arrays as described inembodiments of the present disclosure. In some embodiments, one or moreof gNB 101, gNB 102 and gNB 103 support the codebook design andstructure for systems having 2D antenna arrays.

As described in more detail below, one or more of the gNBs 101-103include circuitry, programing, or a combination thereof, for performingthe audit correction to obtain a result based on a computed score foreach candidate value of the one or more of the BS configurationparameters; generating, based on the result, one or more correctiveactions; and adjusting at least one of the BS configuration parametersbased on the one or more corrective actions.

In certain embodiments, gNB 102 may be connected to the core network 130by a fiber/wired backhaul link. As indicated herein above, gNB 102serves multiple UEs 111-116 via wireless interfaces respectively. Usingthis wireless interface, a UE 116 receives and transmit signals to gNB102. Using signals received from a non-serving gNB 103, a UE 116 mayalso receive signals from a neighboring gNB 103. The core network 130may further include a core network entity (CNE) 135, which responsiblefor the task of site audit correction, as described herein below. Incertain embodiments, the CNE 135 is a base station, such as gNB 103.

Although FIG. 1 illustrates one example of a wireless network, variouschanges may be made to FIG. 1. For example, the wireless network couldinclude any number of gNBs and any number of UEs in any suitablearrangement. Also, the gNB 101 could communicate directly with anynumber of UEs and provide those UEs with wireless broadband access tothe network 130. Similarly, each gNB 102-103 could communicate directlywith the network 130 and provide UEs with direct wireless broadbandaccess to the network 130. Further, the gNBs 101, 102, and/or 103 couldprovide access to other or additional external networks, such asexternal telephone networks or other types of data networks.

FIG. 2 illustrates an example gNB 102 according to embodiments of thepresent disclosure. The embodiment of the gNB 102 illustrated in FIG. 2is for illustration only, and the gNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, gNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of a gNB.

As shown in FIG. 2, the gNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The gNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the wirelessnetwork 100. The RF transceivers 210 a-210 n down-convert the incomingRF signals to generate IF or baseband signals. The IF or basebandsignals are sent to the RX processing circuitry 220, which generatesprocessed baseband signals by filtering, decoding, and/or digitizing thebaseband or IF signals. The RX processing circuitry 220 transmits theprocessed baseband signals to the controller/processor 225 for furtherprocessing.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n. In certainembodiments, the RF transceivers 210 a-210 n perform transmission andreception via radio waves or wired communications. For example,communications may be accomplished via wired connections, optical fibersystems, communication satellites, radio waves, and the like.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the gNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. That is, the controller/processor 225 can perform a blindinterference sensing (BIS) process, such as performed by a BISalgorithm, and decode the received signal subtracted by the interferingsignals. Any of a wide variety of other functions can be supported inthe gNB 102 by the controller/processor 225. In some embodiments, thecontroller/processor 225 includes at least one microprocessor ormicrocontroller

In certain embodiments, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the gNB 102 by thecontroller/processor 225.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also capable of supporting channelquality measurement and reporting for systems having 2D antenna arraysas described in embodiments of the present disclosure. In someembodiments, the controller/processor 225 supports communicationsbetween entities, such as web RTC. The controller/processor 225 can movedata into or out of the memory 230 as required by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the gNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the gNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the gNB102 to communicate with other gNBs over a wired or wireless backhaulconnection. When the gNB 102 is implemented as an access point, theinterface 235 could allow the gNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM. In certain embodiments, a pluralityof instructions, such as a BIS algorithm is stored in memory 230. Theplurality of instructions is configured to cause thecontroller/processor 225 to perform the generation and calibration of asignal strength prediction in a wireless communication system.

As described in more detail below, the transmit and receive paths of thegNB 102 (implemented using the RF transceivers 210 a-210 n, TXprocessing circuitry 215, and/or RX processing circuitry 220) supportgeneration and calibration of a signal strength prediction in a wirelesscommunication system.

Although FIG. 2 illustrates one example of gNB 102, various changes maybe made to FIG. 2. For example, the gNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the gNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350 (or key pad), a display 355, and amemory 360. The memory 360 includes an operating system (OS) 361 and oneor more applications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by a gNB of the wireless network 100. The RFtransceiver 310 down-converts the incoming RF signal to generate anintermediate frequency (IF) or baseband signal. The IF or basebandsignal is sent to the RX processing circuitry 325, which generates aprocessed baseband signal by filtering, decoding, and/or digitizing thebaseband or IF signal. The RX processing circuitry 325 transmits theprocessed baseband signal to the speaker 330 (such as for voice data) orto the processor 340 for further processing (such as for web browsingdata).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for ULtransmission on uplink channel. The processor 340 can move data into orout of the memory 360 as required by an executing process. In someembodiments, the processor 340 is configured to execute the applications362 based on the OS 361 or in response to signals received from gNBs oran operator. The processor 340 is also coupled to the I/O interface 345,which provides the UE 116 with the ability to connect to other devices,such as laptop computers and handheld computers. The I/O interface 345is the communication path between these accessories and the processor340.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 4A is a high-level diagram of transmit path circuitry. For example,the transmit path circuitry may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. FIG. 4B is a high-leveldiagram of receive path circuitry. For example, the receive pathcircuitry may be used for an orthogonal frequency division multipleaccess (OFDMA) communication. In FIGS. 4A and 4B, for downlinkcommunication, the transmit path circuitry may be implemented in a basestation (e.g., gNB 102) or a relay station, and the receive pathcircuitry may be implemented in a user equipment (e.g., user equipment116 of FIG. 1). In other examples, for uplink communication, the receivepath circuitry 450 may be implemented in a base station (e.g., gNB 102of FIG. 1) or a relay station, and the transmit path circuitry may beimplemented in a user equipment (e.g., user equipment 116 of FIG. 1).

Transmit path circuitry comprises channel coding and modulation block405, serial-to-parallel (S-to-P) block 410, Size N Inverse Fast FourierTransform (IFFT) block 415, parallel-to-serial (P-to-S) block 420, addcyclic prefix block 425, and up-converter (UC) 430. Receive pathcircuitry 450 comprises down-converter (DC) 455, remove cyclic prefixblock 460, serial-to-parallel (S-to-P) block 465, Size N Fast FourierTransform (FFT) block 470, parallel-to-serial (P-to-S) block 475, andchannel decoding and demodulation block 480.

At least some of the components in FIGS. 4A 400 and 4B 450 may beimplemented in software, while other components may be implemented byconfigurable hardware or a mixture of software and configurablehardware. In particular, it is noted that the FFT blocks and the IFFTblocks described in this disclosure document may be implemented asconfigurable software algorithms, where the value of Size N may bemodified according to the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and may not be construedto limit the scope of the disclosure. It may be appreciated that in analternate embodiment of the present disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by discrete Fourier transform (DFT) functions andinverse discrete Fourier transform (IDFT) functions, respectively. Itmay be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 4, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 400, channel coding and modulation block 405receives a set of information bits, applies coding (e.g., LDPC coding)and modulates (e.g., quadrature phase shift keying (QPSK) or quadratureamplitude modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 410converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in gNB 102 and UE 116. Size N IFFT block 415 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 420 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 415 toproduce a serial time-domain signal. Add cyclic prefix block 425 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter430 modulates (i.e., up-converts) the output of add cyclic prefix block425 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at the UE 116 after passing throughthe wireless channel, and reverse operations to those at gNB 102 areperformed. Down-converter 455 down-converts the received signal tobaseband frequency and remove cyclic prefix block 460 removes the cyclicprefix to produce the serial time-domain baseband signal.Serial-to-parallel block 465 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 470 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 475 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 480 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of gNBs 101-103 may implement a transmit path that is analogous totransmitting in the downlink to user equipment 111-116 and may implementa receive path that is analogous to receiving in the uplink from userequipment 111-116. Similarly, each one of user equipment 111-116 mayimplement a transmit path corresponding to the architecture fortransmitting in the uplink to gNBs 101-103 and may implement a receivepath corresponding to the architecture for receiving in the downlinkfrom gNBs 101-103.

FIG. 5 illustrates an example antenna blocks 500 according toembodiments of the present disclosure. The embodiment of the antenna 500illustrated in FIG. 5 is for illustration only. FIG. 5 does not limitthe scope of this disclosure to any particular implementation of theantenna 500. In certain embodiments, one or more of gNB 102 or UE 116include the antenna 500. For example, one or more of antenna 205 and itsassociated systems or antenna 305 and its associated systems can beconfigured the same as antenna 500.

Rel.14 LTE and Rel.15 NR support up to 32 CSI-RS antenna ports whichenable an eNB to be equipped with a large number of antenna elements(such as 64 or 128). In this case, a plurality of antenna elements ismapped onto one CSI-RS port. For mmWave bands, although the number ofantenna elements can be larger for a given form factor, the number ofCSI-RS ports—which can correspond to the number of digitally precodedports—tends to be limited due to hardware constraints (such as thefeasibility to install a large number of ADCs/DACs at mmWavefrequencies).

In the example shown in FIG. 5, the antenna 500 includes analog phaseshifters 505, an analog beamformer (BF) 510, a hybrid BF 515, a digitalBF 520, and one or more antenna arrays 525. In this case, one CSI-RSport is mapped onto a large number of antenna elements in antenna arrays525, which can be controlled by the bank of analog phase shifters 505.One CSI-RS port can then correspond to one sub-array which produces anarrow analog beam through analog beamforming by analogy BF 510. Theanalog beam can be configured to sweep 530 across a wider range ofangles by varying the phase shifter bank 505 across symbols orsubframes. The number of sub-arrays (equal to the number of RF chains)is the same as the number of CSI-RS ports N_(CSI-PORT). A digital BF 515performs a linear combination across N_(CSI-PORT) analog beams tofurther increase precoding gain. While analog beams are wideband (hencenot frequency-selective), digital precoding can be varied acrossfrequency sub-bands or resource blocks.

Since the above system utilizes multiple analog beams for transmissionand reception (wherein one or a small number of analog beams areselected out of a large number, for instance, after a trainingduration—to be performed from time to time), the term “multi-beamoperation” is used to refer to the overall system aspect. This includes,for the purpose of illustration, indicating the assigned DL or ULtransmit (TX) beam (also termed “beam indication”), measuring at leastone reference signal for calculating and performing beam reporting (alsotermed “beam measurement” and “beam reporting”, respectively), andreceiving a DL or UL transmission via a selection of a correspondingreceive (RX) beam.

Additionally, the antenna 500 system is also applicable to higherfrequency bands such as >52.6 GHz (also termed the FR4). In this case,the system can employ only analog beams. Due to the O2 absorption lossaround 60 GHz frequency (˜10 decibels (dB) additional loss @100 mdistance), larger number of and sharper analog beams (hence largernumber of radiators in the array) will be needed to compensate for theadditional path loss.

FIG. 6 illustrates examples of a time-division duplex (TDD)communication and a cross-division duplex (XDD) communication accordingto embodiments of the present disclosure. The embodiments of the FDD andXDD communications 600 shown in FIG. 6 are for illustration only. Otherembodiments can be used without departing from the scope of the presentdisclosure.

Modern cellular communication systems typically operate in either TimeDivision Duplexing (TDD) mode or in Frequency Division Duplexing (FDD)mode to accommodate bidirectional communication. In TDD mode, the uplink(UL) 605 and downlink (DL) 610 operate in distinct time slots, whereasin FDD mode they operate in distinct frequency bands.

There are several key tradeoffs between TDD and FDD systems, a prominentexample of which can be seen in uplink coverage. TDD systems bounduplink duration in the time domain, while FDD systems do not. With UEshaving limited power, this can constrain the coverage, especially as theoperating bandwidth (BW) is increased. TDD systems have the advantage ofnot requiring large bandwidth gaps between up and downlink channels.More complicated schemes have provided a way in which these frequencybands can be utilized simultaneously, leveraging the benefits of both:XDD and Full-Duplex (FD) systems.

In FD systems, the uplink and downlink operate in the sametime/frequency resources. This duplexing ultimately leads to extremeself-interference (SI) problems as almost all of a base station'stransmitter power will appear on its uplink receiver. Moreover, theremay also be significant interference from adjacent channel leakage dueto power amplifiers (PAs) in nearby high-power base stations operatingin adjacent channels.

XDD is a new paradigm that provides a unique compromise between FDD andTDD, leveraging the benefits of both. An XDD system is one in whichsimultaneous downlink 615 and uplink 620 are achieved in the samecontiguous band 625, gaining FDD benefits in an unpaired TDD band. Aportion of DL is assigned to UL while the DL is operating andtransmitting adjacent channel power (ACP) in the UL band. Relying on aminimal guard band between uplink and downlink usually is not possibledue to the substantial adjacent channel leakage from the downlinktransmitter interfering with the intended received signal.

In certain embodiments, a SIC technique is required to alleviateself-interference (SI). This cancelation can be done digitally where thesystem aligns and removes an estimate of the transmitted signal in theDL band from the incoming received signal in the UL band. While thesystem knows the original baseband waveform it transmitted, the effectsof multiple analog components and a channel must be accounted for whenestimating the SI. In particular, the PAs introduce extreme nonlineardistortion. Accurately modeling and applying self-interferencecancelation using it is practically challenging, especially inmultiple-in multiple-out (MIMO) systems where there may be manytransmitters and receivers at the base station.

A Generalized Memory Polynomial (GMP) is typically used to model a PA orits inverse for SIC and Digital Predistortion (DPD), respectively. GMPsinclude multiple nonlinearities and memory effects to model a deviceaccurately. However, these models can quickly grow to include hundredsof parameters. Therefore, fitting a GMP to a particular system,especially a MIMO system, has high computational complexity.

While GMPs are popular for DPD applications, they are often notsufficient for SIC applications. In DPD, the goal is to linearize a PAto meet a spectral mask requirement. Hence, the GMP model needs to bejust large enough to accomplish this task. In XDD and FD systems, thegoal is to cancel SI to the receiver noise floor, requiring higheraccuracy in the model and much more complexity. Moreover, to maintainSIC performance near the noise floor, GMP-based systems need frequentupdating of the models as any device operation changes, for example, dueto temperature changes, will degrade SIC performance. This problem isexacerbated in MIMO systems where each transmitter's nonlinearities maybe present on each receiver, requiring multiple high-complexity GMPmodels to need to be maintained and computed.

Removing the self-interference is critical for FD and XDD operations,and there is a need for a low-complexity solution that can do so in MIMOsystems. To address this, certain systems have been developed that useseparate feedback channels along with an array of equalizers, using theequalized feedback signals for SIC. However, that system requires twiceas many high-precision analog to digital converters (ADCs) than wouldtraditionally be needed for any given mobile base station, thusincreasing the system's size and cost. To address this problem,embodiments of the present disclosure provide a new system that strikesa balance between complexity and hardware footprint.

FIG. 7 illustrates an example of a multiple antenna array according toembodiments of the present disclosure. The embodiment of the multipleantenna array 700 shown in FIG. 7 is for illustration only. Otherembodiments can be used without departing from the scope of the presentdisclosure.

In certain embodiments, an XDD system antenna includes a plurality ofantenna ports comprising N transmit antennas and M receive antennas,where M and N are integers. As shown in the example depicted in FIG. 7,in a MIMO system, multiple transmitted downlink (DL) signals caninterfere with a single received uplink (UL) signal.

FIG. 8 illustrates examples of self-interference according toembodiments of the present disclosure. The embodiment of the SI 800shown in FIG. 8 is for illustration only. Other embodiments can be usedwithout departing from the scope of the present disclosure.

In MIMO systems operating in XDD or FD modes, the transmit signal fromeach transmit antenna will interfere with each received signal at eachreceived antenna. Traditional SIC solutions used in single-inputsingle-output (SISO) systems are not applicable because:

Coupling 805 can occur between the DL signal on a transmit antenna toall receive antennas receiving UL 815. Multiple transmit signalsinterfere with the receive antennas with arbitrary time and phaseoffsets. The coupling 805 between a TX antenna and an RX antenna has aunique frequency response that depends on the location of the twoantennas with respect to each other as well as within the antenna panel.Additional crosstalk may exist in the MIMO system that interferes withthe ability to simply use a single input-single output (SISO) approachon all pairs of TX and RX antennas independently.

FIG. 9 illustrates another example of a hybrid digital self-interferencecancelation transceiver according to embodiments of the presentdisclosure. The embodiment of the hybrid digital SIC transceiver 900shown in FIG. 9 is for illustration only. Other embodiments can be usedwithout departing from the scope of the present disclosure.

In certain embodiments, an apparatus, such as gNB 102, includes Ntransmit antennas 905 separated from M receive antennas 910. Theantennas may be partitioned on the same antenna panel or may be locatedon multiple antenna panels. Each transmit path 915 contains a PA withappropriate matching and isolation circuitry before connecting to the TXantenna 905. Additionally, each TX path 915 has a feedback path 920coupled from the output of the PA. Each TX feedback path 920 isconnected to a switch 925, such that receiver circuitry 930 may beswitched between the TX feedback path 9250 and a RX path 935 and RXantenna 910. There is a corresponding RX path for each TX path 915.

Certain embodiments of the present disclosure are configured to operatein two steps. For example, the hybrid digital SIC transceiver 900 canoperate in a modeling process and a SIC operation process.

In the modelling step, the hybrid digital SIC transceiver 900, such asvia a processor, learns a TX path model, which includes any poweramplifiers and other circuitry, between each digital TX signal, such asTX1 940, and each feedback path 920. This step may be performedinfrequently, as it is used only to model the TX paths and associated TXcircuitry, not any dynamic environmental effects. Additionally, themodeling step also requires the receiver (RX path 935 and RX antenna910) to be switched off, which can be time-consuming in a communicationsystem. The preferred model for the TX path 915 and TX circuitry is ageneralized memory polynomial (GMP). There are many other possible waysto model the TX path 915 and TX circuitry that can combine look-uptables with simpler polynomials, such as lower order polynomials, or acombination of connected splines or polynomials behaviorally modellingthe TX response in regions of operation.

In the SIC operation step, the hybrid digital SIC transceiver 900, suchas via a processor, learns the channel between the modelled TX path andeach RX path 935, such that a combination of TX signals (e.g., TX1 940)transformed by the TX path model and subsequently passed through thelearned channel model can be used to estimate the SI at each receiverthat is due to the TX signal leaking into the RX path 935 and associatedRX circuitry through the TX antenna 905 and RX antenna 910. Theestimated SI signal can then be subtracted from the received signal,leaving only the intended up link signal.

TX1 940 is the digital representation of the transmit signal in sampleddomain. After going through any digital predistortion (DPD) 945,interpolation 950, and/or frequency shifting, it is applied to the RFDAC955 that converts it to the RF output signal. This RF signal passesthrough the TX path 915 that consists of anti-aliasing filters, driverstages and the power amplifier.

A coupler 960 is used to extract a small power from the PA output(generally directionally) and is digitized by an RFADC 965 after passingthrough needed filtering 970 and/or gain. This path (RFADC 965, filter970, and numerically controlled oscillator (NCO) & Decimation 975)provides a replica of the signal at the output of the PA to the RX ADC965 (or a dedicated ADC, if necessary). This signal is digitized and canbe used by PA model estimator 980 to create a model of the PA for thepurpose of digital SIC or the inverse model for the purpose of DPD. Analignment circuit 985 adjusts a timing of TX1 940 to match the signaloutput from TX path 915 and enable PA model estimator 980 to estimateSI.

In certain embodiments, the transceiver 900 includes one or more of adigital pre-distortion estimation circuit; up/down conversion mixers;drivers; low noise amplifiers; local oscillator (LO) paths with phaselocked loop (PLL); a radio frequency-analogue to digital converter(RF-ADC); a numerically controlled oscillator (NCO); the equalizer; andthe SIC circuit.

FIG. 10 illustrates another example of a hybrid digitalself-interference cancelation multi-antenna transceiver according toembodiments of the present disclosure. The embodiment of the hybriddigital SIC transceiver 1000 shown in FIG. 10 is for illustration only.Other embodiments can be used without departing from the scope of thepresent disclosure.

In the example shown in FIG. 10, the transceiver 1000 is configured thesame as or similar to transceiver 900; however, transceiver 1000includes N transmit paths and TX antennas. That is, transceiver 1000includes N transmitter circuits coupled to respective TX paths 1005 andTX antenna 1010. The TX paths 1005 can each include a power amplifier.The transmitter circuits include a DPD 1015, Interpolation & NCO 1020,and an RFDAC 1025. Each transmitter circuit receives a respectivetransmit signal, TX1 1030-1, . . . TX N-1 1030-n-1, and TX N 1030-n. Thetransceiver includes receiver circuitry coupled through a switch 1035 torespective RX Path 1040 and RX antennas 1045. The receiver circuitryincludes a SIC 1050, a filter 1055, NCO & Decimation 1060, and an RFADC1065. The output of the RFADC 1065 is coupled to the switch 1035. Theswitch 1035 is configured to change a connection of the receivercircuitry from the RX path 1040 to a feedback (FB) path 1070, which iscoupled to an output of one or more RFDAC 1025. The receiver circuitrycan be coupled through a number of switches 1035 to a number of FB paths1070. The SIC 1050 is coupled to an equalizer 1075, an alignment circuit1080, and a GMP array 1085. Each of the components illustrated in theexample shown in FIG. 10 can be implemented by hardware and circuitryconfigured to perform the respective functions. For example, each of thefilter 1055, alignment circuit 1080, equalizer 1075, GMP circuit 1085,and SIC 1050 can be implemented by suitable, hardware, circuitry, andprocessing circuitry to perform the respective functions. Additionally,each of the filter 1055, alignment circuit 1080, GMP circuit 1085, andequalizer 1075 can include multiple circuits wherein each of thecircuits is coupled to a respective FB path 1030 from each of the TXpaths 1010. For example, the GMP circuit 1085 can include N filters,each coupled to a respective one of the N transmitter circuits; thealignment circuit 1080 can include N alignment circuits, each coupled toa respective output of the N GMP circuits 1085; and the equalizer 1075can include N equalizers, each coupled to a respective output of the Nalignment circuits 1080. In certain embodiments, the transceiver 1000includes one or more of a digital pre-distortion estimation circuit;up/down conversion mixers; drivers; low noise amplifiers; localoscillator (LO) paths with phase locked loop (PLL); a radiofrequency-analogue to digital converter (RF-ADC); a numericallycontrolled oscillator (NCO); the equalizer; and the SIC circuit.

The transceiver 1000 is configured to receive and transmit OFDM signals.In certain embodiments, such as in XDD communication, the transceiver1000 is configured to concurrently operate in the UL and the DL. In suchscenarios, leakage from a signal transmitted by the transmit canoverlap, in time and frequency bands, with a signal received by thereceive path. For example, if the TX antenna 1010 is transmitting in theDL and the RX antenna 1045 is concurrently receiving in the UL, the RXpath 1040 may also receive a portion of the DL signal that is leakingover into the time and frequency bands being used for the UL since thereis no guard band to separate the DL and UL communications. The RX path1040 is configured to receive a receive signal and can include a lownoise amplifier, a down-conversion mixer, an analog baseband filter, ananalog gain, and an A/D converter.

The transceiver 1000 is coupled to, or includes, a processor 1090. Forexample, the processor 1090 can be the same as, or similar to,controller/processor 225 or processor 340. The processor 1090 isconfigured to set or revise one or more parameters of the equalizer1075. For example, the processor 1090 is configured to set one or morecoefficients of an equalizer function performed or used by the equalizer1075.

The receiver circuits are switched to the PA feedback to learn GMP-basedPA models for each transmit signal one at a time. For example, theprocessor 1090 can operate switch 1035 to turn off RX path 1040 and RXantenna 1045 and connect the receiver circuit to FB path 1070. In analternative embodiment, a dedicated FB path 1070 with its own RFADCcould be used instead of sharing the RX path ADC 1065.

Individual least-squares problems are formulated, such as by processor1090 or GMP array 1085, to learn each GMP-based PA model using thedigital transmit signals and received PA feedback signals. In analternative embodiment, a mean square or another method could be used toreduce the error between the model and the measured data.

The RX paths are switched to receive over the air transmissions forstandard RX operation. For example, the processor 1090 can operateswitch 1035 to turn on RX path 1040 and RX antenna 1045 and disconnectthe receiver circuit from FB path 1070.

To estimate the self-interference (SI), the processor 1090 transmits aknown signal on all transmitters simultaneously. For example, theprocessor 1090 transmits a first signal 1030-1 through 1030-n on alltransmitters simultaneously. The processor 1090 can transmit the samefirst signal on all the TX paths 1005 or the processor 1090 can transmita different known signal on different ones of the TX paths 1005. Forexample, TX1 1030-1 can be the same as the TX N-1 1030-n-1; butdifferent from the TX N 1030-n. Alternatively, TX1 1030-1 can bedifferent from TX N-1 1030-n-1 and different from TX N 1030-n.

In certain embodiments, the processor 1090 formulates a globalleast-squares problem to jointly learn equalizers 1075, and respectiveequalizer functions, between the digital transmit signals passed throughtheir individual PA models and the signals received from thecorresponding receive paths to optimally learn the equalizers 1075. Theprocessor 1090 models the equalizers 1075 after the individualinterference channels from each modeled transmitter (transmit circuitry)to each receiver (receive circuitry). The learned channel may include avariety of standard channel effects such as multi-tap effects due tomultiple reflections.

The modelled transmit signals are passed through these learnedequalizers 1075 in the digital domain to estimate the self-interferenceon each received signal. The SIC circuit 1050 subtracts the SI estimatefrom each receiver, or applying SIC to produce a residual signal. Theresidual signal corresponds to the intended uplink signal on eachreceiver and will have improved SINR and, consequently, improved channelcapacity.

In certain embodiments, the transceiver 1000 is configured to use acombination of modelled PA transmit signals and equalizers to canceleach received interference signal. The transceiver 1000 is configured touse a hybrid GMP/Equalizer process by first performing a modellingprocess and then performing an SIC Operation process.

GMP Learning (Modelling)

Herein, the baseband equivalent transmit signal on antenna i isrepresented by the discrete signal x_(i)[n], where n indexes the samplesof the signal. Similarly, {tilde over (x)}_(i)[n] and y_(j)[n] representthe estimated PA output signal for the ith PA and the receive signal forthe jth receiver port, respectively. In the modelling step, theprocessor learns a GMP, g_(i)(.), representing the transfer functionfrom x_(i)[l] to {tilde over (x)}_(i)[l]. The GMP is given as Equation1:

{tilde over (x)}[n]=g _(i)(x[n])=Σ_(p∈P) _(a) Σ_(v∈V) _(a) α_(i,p,v)x[n−v]|x[n−v] ^(p−1)+Σ_(p∈P) _(b) Σ_(v∈V) _(b) Σ_(l∈L) _(b) α_(i,p,v,l)x[n−v]|x[n−v−l] ^(p−1)+Σ_(p∈P) _(c) Σ_(v∈V) _(c) Σ_(l∈L) _(c)α_(i,p,v,l) x[n−v]|x[n−v+l]| ^(p−1)   (1)

The processor 1090 learns the GMP coefficients via the followingoptimization for each transmit signal, as shown in Equation 2:

$\begin{matrix}{\alpha_{i} = {\underset{\alpha_{i}}{argmin}{{{y_{i}\lbrack n\rbrack} - {g_{i}\left( {x\lbrack n\rbrack} \right)}}}}} & (2)\end{matrix}$

Equalizer Learning (SIC Operation)

Once the GMP models for each transmit path have been obtained, theprocessor 1090 learns FIR filters of length K, h_(ij)[k], that minimizesthe squared error between all N PA estimated output signals and the jthreceive signal. Equalizer formulation is given by Equation 3:

$\begin{matrix}{{h_{i,j}\lbrack k\rbrack} = {\underset{h_{i,j}\lbrack k\rbrack}{argmin}{{{{y_{j}\lbrack n\rbrack} - {\sum_{i = 1}^{N}{{h_{i,j}\lbrack k\rbrack}*{{\overset{\sim}{x}}_{i}\lbrack n\rbrack}}}}}^{2}.}}} & (3)\end{matrix}$

In certain embodiments, the least-squares is solved over all filtersh_(ijk)[k] simultaneously. To solve this, the processor 1090 formulatesthe system in an equivalent matrix formulation and utilizes theleast-squares solution. For the matrix based formulation, each signal iswritten as an M×1 vector of samples, x_(i)=[x(0) x(1) . . . x(M−1)]^(T).For notational convenience, a signal x[n] is considered to be delayed byk samples as x_(i) ^((k))=[0_(k) x(0) x(1) . . . x(M−1−k)]^(T), where0_(k) represents the 1×k dimensional zero vector. This yields theoptimization problem as shown in Equation 4:

$\begin{matrix}{{h_{j} = {\underset{h_{j}}{argmin}{{y_{j} - {\overset{\sim}{X}h_{j}}}}}},} & (4)\end{matrix}$

In Equation 4, h_(j)=[h_(1,j) . . . h_(N,j)]^(T) is the concatenation ofall filter coefficients for all N GMP output signals to the jth receivesignal and {tilde over (X)} is constructed as shown in Equation 5:

{tilde over (X)}=[{tilde over (x)} ₁ ⁽⁰⁾ . . . {tilde over (x)} ₁^((K−1)) {tilde over (x)} ₂ ⁽⁰⁾ . . . {tilde over (x)} _(N) ^((K−1))].  (5)

With this, the solution is given through canonical least-squares asshown in Equation 6:

h _(j)=({tilde over (X)}^(H) {tilde over (X)})⁻¹ {tilde over (X)} ^(H) y_(j)   (6)

In Equation 6, H represents the Hermitian transpose. This solution issolved for all j. Once solved, the concatenated solution can beseparated into individual impulse responses h_(ij)[k] for all i.

Application (SIC Operation)

Once learned, each FIR filter can be applied to compute the jthresidual, u_(j)[n], on each receive signal as shown in Equation 7:

u _(j) [n]=y _(i) [n]−Σ _(i=1) ^(N) h _(i,j) [k]*{tilde over (x)} _(i)[n].   (7)

Each residual is the received signal vector once the SI has beenremoved.

Therefore, according to certain embodiments, in the Hybrid GMP/EqualizerSIC, there are two operating modes: 1) Modelling and 2) SIC Operation.Modelling mode is performed infrequently to build relatively static GMPmodels for the system's transmit paths. While in Modelling mode, thereceive antennas will not be active, instead the receive ADC willcapture the transmit path feedback signal. The SIC Operation mode is thestandard operating procedure, where the channel equalizers are updatedas necessary and the SIC is performed. This mode is used while operatingthe communication system normally, transmitting and receiving user data.

FIG. 11 illustrates a state machine for operating mode transitionsaccording to embodiments of the present disclosure. The embodiment ofthe state machine 1100 shown in FIG. 11 is for illustration only. Otherembodiments could be used without departing from the scope of thepresent disclosure.

In operation state 1105, the system starts up. After startup in, thesystem proceeds to modeling in the modeling state 1110.

FIG. 12 illustrates a modeling process according to embodiments of thepresent disclosure. While the flow chart depicts a series of sequentialsteps, unless explicitly stated, no inference should be drawn from thatsequence regarding specific order of performance, performance of stepsor portions thereof serially rather than concurrently or in anoverlapping manner, or performance of the steps depicted exclusivelywithout the occurrence of intervening or intermediate steps. The processdepicted in the example depicted is implemented by a transmitter andprocessor circuitry in, for example, a base station. Process 1200 can beaccomplished by, for example, gNB 102. The process 1200 can be performedin operation state 1110.

In Modelling, there are two main blocks: TX Path Estimation 1305 and GMPArray 1310. FIG. 13 illustrates an example modelling system diagramaccording to embodiments of the present disclosure. The embodiment ofthe modelling system 1300 shown in FIG. 13 is for illustration only.Other embodiments could be used without departing from the scope of thepresent disclosure. In certain embodiments, one or more processors, suchas processor 1090 performs one or more functions of one or more of TXPath Estimation 1305 and GMP Array 1310.

In operation 1205, the receiver paths are set to feedback. That is, theprocessor 1090 operates switch 1035 to turn off RX path 1040 and RXantenna 1045. The switch 1035 is operated to select a first feedbackpath 1070. In operation 1210, the processor 1090 transmits a firstsignal (TX signal) on the selected TX port. In operation 1215, a secondsignal (RX signal) is received on all RX ports. The second signals arealigned to the first signal.

In operation 1225, a solution for a least squares (LS) estimate for theTX and RX signals is obtained. The TX Path Estimation 1305 obtains thedigital TX signals 1315 and FB receive signals 1320. The TX PathEstimation 1305 uses each digital TX signal 1315 and each fed back TXPath signal 1320 to create a forward path model that can transform thedigital transmit signal 1315 into an estimate of the signal at theoutput of the TX Path 1325. The TX Path Estimation 1305 generates GMPmodels for each TX path 1325. In certain embodiments, the forward pathmodel is created by estimating a number of non-linear components, eachof the non-linear components corresponding to a respective transmit pathfor the first number of transmit antennas; and calculate one or morecoefficients of the equalizer function by calculating a number ofcoefficients for the equalizer function for each of the second number ofreceive antennas. That is, the forward path model is configured to modelis configured to model the non-linear component corresponding to thefirst transmit path in the transceiver using one or more of: ageneralized memory polynomial (GMP), a simplified MP, dividing operatingregions into sections, or a hybrid scheme using a look-up table andlower order polynomials.

The GMP Array 1310 receives the GMP models 1330 output by the TX PathEstimation 1305. In Modelling mode, the GMP Array 1310 inputs thegenerated GMP models for each TX Path 1325 and stores them for use inthe SIC Operation Mode, in the operation state 1115. Therefore, N TXpaths 1325 contain N GMP models 1330, one for each PA.

In operation 1225, the forward path model is updated and the TX portincremented. In operation 1230, it is determined whether all models havebeen learned. For example, the processor 1090 can determined whether amodel has been learned for each transmitter with respect to eachreceiver. If it is determined that all forward path models have not beenlearned, the process proceeds to operation 1210. If it is determinedthat all forward path models have been learned, the process proceeds tooperation 1235 to switch to the operation mode in operation state 1110.

The purpose of Modelling Mode is to learn TX model (including PA) suchthat the digitally transmitted signals can be passed through the TXmodel to produce a close replica of the TX Path output. This transformmodel can be used to account for any number of RF operations in thetransmit path, including filters, mixers (if used in a conventional TX),power amplifiers, and the like, that add nonlinearity. Modelling moderequires that either a dedicated FB path 1070 converts the signal at PAoutput to digital form, or that some resources in the receiver arereused, such as one or more stages of amplifiers and filters to beconnected to the coupler at the PA output. In this case, the receiverwill be used to digitize the feedback signal at PA coupler. In certainembodiments, the RX is reconfigured to normal mode where it accesses theRX signal at the antenna.

To learn each forward path model, the TX Path Estimation block willtransmit through a single TX path at a time, then formulate an LSproblem to map the digital transmit signal to the received TX Pathoutput signal. This process is repeated for each TX Path. Thecoefficients learned from each LS fit are then passed to the GMP Array1310, where they are stored for use in SIC Operation Mode. This steplearns the nonlinear model of each TX path.

SIC Operation

FIG. 14 illustrates a process for self-interference cancelationaccording to embodiments of the present disclosure. While the flow chartdepicts a series of sequential steps, unless explicitly stated, noinference should be drawn from that sequence regarding specific order ofperformance, performance of steps or portions thereof serially ratherthan concurrently or in an overlapping manner, or performance of thesteps depicted exclusively without the occurrence of intervening orintermediate steps. The process depicted in the example depicted isimplemented by a transmitter and processor circuitry in, for example, abase station. Process 1200 can be accomplished by, for example, gNB 102.The process 1200 can be performed in operation state 1110.

After learning the PA model, the channels between each TX Path outputsignal and each RX signal are learned. This step is performed to be ableto reproduce the TX leakage in the RX for the purpose of SIC.

In SIC Operation, there are four main blocks: GMP Array 1505, Equalizer(EQ) Estimation 1510, EQ Array 1515, and SIC 1520. FIG. 15 illustratesan example SIC Operation System diagram according to embodiments of thepresent disclosure. The embodiment of the SIC Operation System 1500shown in FIG. 15 is for illustration only. Other embodiments could beused without departing from the scope of the present disclosure. One ormore components illustrated in FIG. 15 may correspond to one or morecomponents in FIGS. 9, 10, and 13. For example, GMP Array 1505 can bethe same as, or similar to, GMP array 1085 or GMP array 1310; EQEstimation 1510 and EQ Array 1515 can be the same as, or similar to,Equalizer 1075; and SIC 1520 can be the same as, or similar to, SIC1050. In certain embodiments, one or more processors, such as processor1090 performs one or more functions of one or more of GMP Array 1505,Equalizer (EQ) Estimation 1510, EQ Array 1515, and SIC 1520.

In operation 1405, the RX path and RX antenna are coupled to thereceiver. For example, the processor 1090 can operate switch 1035 toturn on RX path 1040 and RX antenna 1045. Upon entering SIC Operationmode from Modelling Mode, the RX Paths need to be switched such thatthey are connected to the receive antennas rather than the feedback fromTX Path. Additionally, before SIC can be performed, the equalizers needto be learned. In operation 1410, a determination is made regardingwhether all the equalizers have been learned. If all the equalizers havenot yet been learned, the process proceeds to operation 1415 in which,to learn the coefficients for each equalizer, the system firstbroadcasts signals on all transmitters in the array. In operation 1420,the transmit signals are received on all RX ports. The transmit signalsare fed through the GMP array 1505, such that the resulting transformedsignals capture all the nonlinearities created by the power amplifierand/or other components in the transmit path. In operation 1425, alltransformed transmit signals and RX paths are sent to the EQ Estimation1515, where a least squares estimation is performed to jointly learnequalizers from each TX path (using the digitally transformed signals)to each RX path. Each equalizer here is a learned interference channelbetween each transformed transmit signal to each received signal. Onceeach equalizer is learned through the LS, the EQ Array 1515 is updated.

In operation 1430, the process proceeds to the application phase. Duringthe application phase, all the transformed transmit signals are passedthrough each of the equalizers and linearly combine them to create atotal estimated self-interference (SI) signal for each RX port. That is,in operation 1430, each TX signal is sent through the TX path model. TheGMP Array 1505 inputs digital TX signals 1525 and outputs digital(feedback) signals 1530 that reflect the modelled transmitter path. Themodels themselves are learned in the Modelling mode. In operation 1435,each TX path estimate is sent through the equalizers (EQ Array 1515).The EQ Estimation 1510 inputs both FB signals 1530 and RX signals 1535,estimates the channel transformation (equalizer) between each FB signal1530 and RX signal 1535, and outputs the ensemble of learned equalizers1540. The EQ Array 1515 inputs FB signals 1530 and outputs an SIEstimate 1545 for each RX signal. In operation 1440, each SI estimate issubtracted from the RX port and each residual signal is output inoperation 1445. The SIC 1520 subtracts each input SI Estimate 1545 fromeach RX signal and outputs the interference-free RX signals, which areResiduals 1550. That is, the SI signals are passed to the SIC 1520 wherethe SI Estimate for each RX signal is subtracted out. The SIC 1520 thenreturns the residuals where the SI signals have been removed. Theresidual leftover contains only the uplink signal with an improved SINR.

In certain embodiments, the transceiver includes conventional TX and RXwith baseband filters, up/down-conversion mixers, drivers/LNA, localoscillator (LO) path with PLL. In certain embodiments, the hybridGMP/Equalizer transceiver uses computational simplifications of theestimators, such as Mean Square (LMS) vs recursive least squares (LS).Certain embodiments use simplifications of the GMP, such as by using MPor dividing operating region into sections in which each section can usea simplified lower complexity GMP or MP, or hybrid schemes that use LUTand lower polynomials orders. In certain embodiments, the equalizer isconfigured to provide real-time output at speed, while computation ofequalizer can be done in a processor. In certain embodiments, the PAmodel is updated if it is expected to change, such as due to change intemperature. In certain embodiments, the channel equalizer is updated bycalculating it again, if it is expected to have changed for some reason.

The above flowcharts illustrate example methods that can be implementedin accordance with the principles of the present disclosure and variouschanges could be made to the methods illustrated in the flowchartsherein. For example, while shown as a series of steps, various steps ineach figure could overlap, occur in parallel, occur in a differentorder, or occur multiple times. In another example, steps may be omittedor replaced by other steps.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims. None of the description in this application should be read asimplying that any particular element, step, or function is an essentialelement that must be included in the claims scope.

What is claimed is:
 1. An apparatus comprising: a transceiver configuredto communicate via an uplink channel and a downlink channelconcurrently; a first number of transmit antennas; a second number ofreceive antennas; an equalizer configured to, for at least one receiveantenna of the second number of receive antennas, apply a forward pathmodel including a non-linear component corresponding to a transmit pathin the transceiver, and apply an equalizer function to a first signal tobe transmitted by at least one transmit antenna of the first number oftransmit antennas to determine a self-interference (SI) estimate; andself-interference cancel (SIC) circuitry configured to, for the at leastone receive antenna of the second number of receive antennas, subtractthe SI estimate from the signal received via at least one receiveantenna of the second number of receive antennas to obtain an residualsignal.
 2. The apparatus of claim 1, further comprising a processorconfigured to: create the forward path model by estimating a number ofnon-linear components, each of the non-linear components correspondingto a respective transmit path for the first number of transmit antennas;and calculate one or more coefficients of the equalizer function bycalculating a number of coefficients for the equalizer function for eachof the second number of receive antennas.
 3. The apparatus of claim 2,further comprising a number of switches, each of the switches coupledbetween a respective receiver circuitry and a respective receive path,wherein the respective receiver circuitry comprises the SIC circuitryand the receive path is coupled to the at least one receive antenna, andwherein to estimate the number of non-linear components, the processoris configured to: disconnect, via a first switch of the number ofswitches, a first receive path and the at least one receive antenna;obtain the first signal to be transmitted through a first transmit pathand a first transmit antenna of the first number of transmit antennas;align the first signal with an output signal obtained at an input of thefirst transmit antenna; and calculate, based on the first signal and theoutput signal, the coefficients to model the first transmit path.
 4. Theapparatus of claim 3, wherein the forward path model is configured tomodel the non-linear component corresponding to the first transmit pathin the transceiver using one or more of: a generalized memory polynomial(GMP), a simplified MP, dividing operating regions into sections, or ahybrid scheme using a look-up table and lower order polynomials.
 5. Theapparatus of claim 3, wherein the equalizer is configured to determinethe SI estimate using one of: least means square (LMS) or recursiveleast-squares.
 6. The apparatus of claim 2, wherein the processor isconfigured to update the one or more coefficients.
 7. The apparatus ofclaim 1, wherein one or more of a receiver circuitry or a transmittercircuitry comprises one or more of: a coupler; a digital pre-distortionestimation circuit; up/down conversion mixers; drivers; low noiseamplifiers; local oscillator (LO) paths with phase locked loop (PLL); aradio frequency-analogue to digital converter (RF-ADC); a numericallycontrolled oscillator (NCO); the equalizer; and the SIC circuit.
 8. Amethod comprising: transmitting, by a transceiver configured to transmitan uplink channel and a downlink channel concurrently, one or moresignals, the transceiver comprising: a first number of transmitantennas; and a second number of receive antennas; and for at least onereceive antenna of the second number of receive antennas: applying aforward path model including a non-linear component corresponding to atransmit path in the transceiver, and applying an equalizer function toa first signal to be transmitted by at least one transmit antenna of thefirst number of transmit antennas determine a self-interference (SI)estimate; and subtracting, in a self-interference cancel (SIC)circuitry, the SI estimate from the signal received via at least onereceive antenna of the second number of receive antennas to obtain anresidual signal.
 9. The method of claim 8, further comprising: creatingthe forward path model by estimating a number of non-linear components,each of the non-linear components corresponding to a respective transmitpath for the first number of transmit antennas; and calculating one ormore coefficients of the equalizer function by calculating a number ofcoefficients for the equalizer function for each of the second number ofreceive antennas.
 10. The method of claim 9, wherein estimating thenumber of non-linear components further comprises: disconnecting, via aswitch, a first receive path and the at least one receive antenna;obtaining the first signal to be transmitted through a first transmitpath and a first transmit antenna of the first number of transmitantennas; aligning the first signal with an output signal obtained at aninput of the first transmit antenna; and calculating, based on the firstsignal and the output signal, the coefficients to model the firsttransmit path.
 11. The method of claim 10, further comprising:generating the forward path model by modelling the non-linear componentcorresponding to the first transmit path in the transceiver using one ormore of: a generalized memory polynomial (GMP), a simplified MP,dividing operating regions into sections, or a hybrid scheme using alook-up table and lower order polynomials.
 12. The method of claim 10,further comprising estimating the SI estimate using one of: least meanssquare (LMS) or recursive least-squares.
 13. The method of claim 9,further comprising updating the one or more coefficients.
 14. The methodof claim 8, further comprising wherein one or more of a receivercircuitry or a transmitter circuitry comprises one or more of: acoupler; a radio frequency (RF) receiver path; and a digitalpre-distortion estimation circuit; up/down conversion mixers; drivers;low noise amplifiers; local oscillator (LO) paths with phase locked loop(PLL); a radio frequency-analogue to digital converter (RF-ADC); anumerically controlled oscillator (NCO); an equalizer; and the SICcircuit.
 15. A non-transitory computer readable medium comprising aplurality of instructions that, when executed by at least one processor,cause the processor to: transmit, via a transceiver configured totransmit an uplink channel and a downlink channel concurrently, one ormore signals, the transceiver comprising: a first number of transmitantennas; and a second number of receive antennas; and for at least onereceive antenna of the second number of receive antennas: apply aforward path model including a non-linear component corresponding to atransmit path in the transceiver and apply an equalizer function to afirst signal to be transmitted by at least one transmit antenna of thefirst number of transmit antennas to determine a self-interference (SI)estimate; and subtract, in a self-interference cancel (SIC) circuitry,the SI estimate from the signal received via at least one receiveantenna of the second number of receive antennas to obtain an residualsignal.
 16. The non-transitory computer readable medium of claim 15,wherein the plurality of instructions is further configured to cause theat least one processor to: create the forward path model by estimating anumber of non-linear components, each of the non-linear componentscorresponding to a respective transmit path for the first number oftransmit antennas; and calculate one or more coefficients of theequalizer function by calculating a number of coefficients for theequalizer function for each of the second number of receive antennas.17. The non-transitory computer readable medium of claim 16, wherein theplurality of instructions is further configured to cause the at leastone processor to estimate the number of non-linear components by:disconnecting, via a switch, a first receive path and the at least onereceive antenna; obtaining the first signal to be transmitted through afirst transmit path and a first transmit antenna of the first number oftransmit antennas; aligning the first signal with an output signalobtained at an input of the first transmit antenna; and calculating,based on the first signal and the output signal, the coefficients tomodel the first transmit path.
 18. The non-transitory computer readablemedium of claim 17, wherein the plurality of instructions is configuredto cause the at least one processor to generate the forward path modelby modelling the non-linear component corresponding to the firsttransmit path in the transceiver using one or more of: a generalizedmemory polynomial (GMP), a simplified MP, dividing operating regionsinto sections, or a hybrid scheme using a look-up table and lower orderpolynomials, and wherein the plurality of instructions is configured tocause the at least one processor to estimate the SI estimate using oneof: least means square (LMS) or recursive least-squares.
 19. Thenon-transitory computer readable medium of claim 16, wherein theplurality of instructions is further configured to cause the processorto update the one or more coefficients.
 20. The non-transitory computerreadable medium of claim 15, wherein one or more of a receiver circuitryor a transmitter circuitry comprises one or more of: a coupler; a radiofrequency (RF) receiver path; and a digital pre-distortion estimationcircuit; up/down conversion mixers; drivers; low noise amplifiers; localoscillator (LO) paths with phase locked loop (PLL); a radiofrequency-analogue to digital converter (RF-ADC); a numericallycontrolled oscillator (NCO); an equalizer; and self-interference cancel(SIC) circuitry.